Assessment of the impact of Tianwan Nuclear Power Plant on the adjacent marine ecosystem

Based on the monitoring data of 137Cs and 90Sr in Tian Bay in 2005-2023, the impacts of the operation of Tianwan Nuclear Power Plant on the marine ecosystem were assessed. The 137Cs and 90Sr activity concentrations in the seawater and sediment varied within the background ranges. The radiation dose rates derived from 137Cs and 90Sr for the marine organisms ranged from 2.4 × 10-5 to 2.2 × 10-4 nGy/h, it was far below the most conservative screening dose rate (10 μGy/h). The committed effective dose for humans was 0.070-0.094 μSv, 1/1500th of the world's mean annual effective dose (0.12 mSv) from ingesting food containing uranium and thorium series nuclides. Radiation risk assessment showed no radiation risk for the long-term discharge of nuclear wastes in the future. Overall, the long-term normal operation of TNPPs has almost no radiation impact on the adjacent marine ecosystem.

Half-century trends of radioactivity in fish from Danish areas of the North Sea, Kattegat, and Baltic Sea

This work reports comprehensive time-series datasets over the past 50 years for natural (210Po) and anthropogenic (134Cs and 137Cs) radionuclides in three fish species (cod, herring and plaice) from Danish marine areas covering the North Sea, Kattegat, and Baltic Sea. Impact from the global fallout of atmospheric nuclear weapons testing, radioactive discharges from the European nuclear reprocessing plants and release from Chernobyl accident are clearly detected in the fish samples. While 210Po concentrations in each fish species demonstrated comparable levels across the three regions without notable temporal trends, significantly higher median 210Po concentration was observed in the lower trophic level fish, namely herring and plaice, compared to cod. In contrast, 137Cs concentrations in all three species steadily decrease over time after the Chernobyl-attributed peaks in late 1980s in the entire study area, whereas 137Cs always demonstrated higher concentrations in cod than herring and plaice. Our calculated concentration factors (CFs) for 137Cs in this work indicate that the mean CFs for 137Cs over the past 50 years are significantly different across the three species, following the order of cod < herring < plaice. Based on the time-series data, ecological half-lives (Teco) of 137Cs in fish from Danish marine areas were estimated to evaluate the long-term impact of anthropogenic radioactive contamination in different regions. Our results indicate no significant difference in Teco across different fish species, whereas the weighted mean Teco for fish in the Baltic Sea (29.3 ± 3.9 y) is significantly longer than those of the North Sea (9.8 ± 0.9 y) and Kattegat (11.7 ± 1.2 y), reflecting the strong 'memory effect' of the Baltic Sea due to its slow water renewal. However, the dose assessment demonstrates that the contribution of the natural radionuclide 210Po to ingestion dose from fish consumption is 1-2 order of magnitude higher compared to that of 137Cs.

Experiences from the ARGOS user group nuclear emergency exercise

The Accident Reporting and Guiding Operational System (ARGOS) is a decision support system used to assist in the Emergency Preparedness and Response (EPR) to nuclear and radiological incidents. The ARGOS user group has been formed that is made up of government agencies across many countries that have a role in EPR to nuclear and radiological incidents. In 2020, a desktop exercise was organised for the members of the ARGOS user group. The exercise involved two hypothetical accidents at different times on the same date, namely a radiological release from a floating nuclear power plant (NPP) off the Norwegian coast and from the Loviisa NPP in Finland. The objectives of the exercise were to train and increase knowledge of the ARGOS system, to perform a comparison of model outputs, and to compare the recommendations of protective actions. In the case of the floating NPP the source term was provided, while in the Loviisa NPP scenario the participants were required to provide their own source term based on a description of the accident. The results on radiological consequences based on dispersion modelling, protective actions, source terms and dispersion modelling settings were collected from participants. A comparison was made between each of these reported aspects. In general, it was found that there was general agreement between the results for the floating nuclear power plant scenario in the sense of plume direction and extent, while in the case of the Loviisa NPP scenario, there was much greater variation, with the difference in source term estimates between the participants being an influencing factor. The participants acknowledged that taking part in an exercise of this nature increased their knowledge and understanding about using decision support tools such as ARGOS in planning and responding to nuclear and radiological emergencies.

Assessment of natural radioactivity in Moroccan bottled drinking waters using gamma spectrometry

Radioactive elements and their impact on the environment and the food chain, including humans, are a matter of major concern, for which appropriate investigations should be performed. The priority is to examine the concentration of radioactive substances in mineral and bottled spring water. This task aims to analyze the quality of 12 conditioned mineral waters by determining their main radionuclides concentrations, such as 238U, 232Th, and 40K. The identification and the quantification of these radionuclides are carried out by their progeny (except the 40K) by using a NaI(Tl) detector coupled with a multichannel analyzer (MCA) and connected to a computer. The activity measured in all samples varied from 0.95 to 3.38 mBq.L-1 with an average of 1.94 mBq.L-1; from 1.55 to 3.56 mBq.L-1 with an average of 2.46 mBq.L-1; and from 200.68 to 269.19 mBq.L-1 with an average of 236.6 mBq.L-1, for 238U, 232Th, and 40K, respectively. To compare the combined radiological effects of radionuclides present in water, a particular factor Ra(eq) is used. This study showed that the maximum value of Ra(eq) is 27.54 mBq.L-1, which is far below the activity limit of 370 mBq.year-1 set by the Organization of Economics and Development (OECD). Concerning the effective annual dose, the following maximums were measured: 1.61 μSv.year-1, 1.133 μSv.year-1, and 0.925 μSv.year-1 for infants, children, and adults, respectively. These values are even smaller than the dose recommended by the WHO which is 100 μSv.year-1. Regarding the excess lifetime cancer risk index, a maximum of 5.63 × 10-6 is found. This index value is still less than that proposed by James, namely 2.5 × 10-3. Thus, the quality of the studied samples respects the radiological international safety and health limits.

Po-210 activity concentrations in wild and farmed fish from the Aegean Sea and Sea of Marmara and dose assessment to consumers

Polonium (210Po) is the major contributor (with approximately 90%) to the radiation dose from radionuclides contained in the human diet, and it is mostly associated with seafood. This study presents 210Po activity concentrations in the tissues of 16 fish species from the Aegean Sea and Sea of Marmara. Among all species investigated, the highest 210Po activity concentration was 4450 ± 33 Bq kg-1 dry weight (dw) in the digestive tract of anchovy (Engraulis encrasicolus), and the lowest 210Po activity concentration was 1.3 ± 0.6 Bq kg-1 (dw) in the muscle tissue of the thornback ray (Raja clavata). Significant differences in 210Po concentrations were consistently found among the tissues of fish (P < 0.05). In general, the prominent accumulation of 210Po was observed in the digestive tract and liver while the muscle tissue generally displayed the lower concentrations. Polonium concentrations in the internal organs, such as muscle and liver, were related to the feeding ecology of fish and thus are a consequence of 210Po transfer in the food chain rather than 210Po uptake from water. The average 210Po concentration in fish filet was 54.1 Bq kg-1 dw and to attain the recommended limit for the annual committed effective dose (1 mSv year-1) would require the consumption of 1024 kg of mixed fish filet in 1 year, which is unlikely to happen. The highest 210Po activity concentration in the edible part of fish (filet) was determined in the anchovy (E. encrasicolus) but to reach the 1 mSv year-1 limit would require still the consumption of 7.1 kg year-1 of anchovy filet. Similar size specimens of wild and farmed fish, Dicentrarchus labrax and Sparus aurata, were analyzed to assess the differences in 210Po concentrations. Polonium concentrations in the wild fish were several-fold higher than in farmed specimens, these ones fed with fish feed with 210Po content lower than natural food in the sea. Therefore, the current trend of increasing the consumption of seafood from aquaculture seems to be reducing the radiation exposure to 210Po in the human diet that is considered beneficial to public health.

Using energy expenditure to estimate the minute ventilation and inhaled load of air pollutants: a pilot survey in young Chinese adults

Existing equations to estimate ventilation (VE) may not represent the Chinese population. The objective is to develop regression equations to predict the basal metabolic rate (BMR) for ventilation estimation. 80 participants underwent the incremental tests on a bicycle ergometer, wearing a fitted facial mask with an airflow sensor connected to the cardiopulmonary gas analyzer, where the energy expenditure, metabolic factors and VE were monitored simultaneously. Linear regression models were established between BMR and body weight, which were used to estimate energy expenditure and VE. Extrapolation of the regression model was evaluated by the five-fold cross-validation. And we also assessed the inhaled load of air pollutants in subgroups at the same exposure levels. Regression models for males and females were BMR (kJ/d) = 107.58 × weight (kg)-172.61 and BMR (kJ/d) = 105.61 × weight (kg)-26.94, respectively. The model showed good fitness between the measured and predicted VE. Differences between the measured and predicted VE of this model are smaller than that of other models. There were significant differences in inhaled load participants in the same exposure concentrations. The regression model showed that weight and BMR are highly correlated and can be used to estimate individual VE.

Simulating the impact of particulate matter exposure on health-related behaviour: A comparative study of stochastic modelling and personal monitoring data

Epidemiological and exposure studies concerning particulate matter (PM) often rely on data from sparse governmental stations. While low-cost personal monitors have some drawbacks, recent developments have shown that they can provide fairly accurate and fit-for-purpose data. Comparing a stochastic, i.e., agent-based model (ABM), with environmental, biometric and activity data, collected with personal monitors, could provide insight into how the two approaches assess PM exposure and dose. An ABM was constructed, simulating a PM exposure/dose assessment of 100 agents. Their actions were governed by inherent probabilities of performing an activity, based on population data. Each activity was associated with an intensity level, and a PM pollution level. The ABM results were compared with real-world results. Both approaches had comparable results, showing similar trends and a mean dose. Discrepancies were seen in the activities with the highest mean dose values. A stochastic model, based on population data, does not capture well some specifics of a local population. Combined, personal sensors could provide input for calibration, and an ABM approach can help offset a low number of participants. Implementing a function of agents influencing others transport choice, increased the importance of cycling/walking in the overall dose estimate. Activists, agents with an increased transport influence, did not play an important role at low PM levels. As concentrations rose, higher shares of activists (and their influence) caused the dose to increase. Simulating a person's PM exposure/dose in different scenarios and activities in a virtual environment provides researchers and policymakers with a valuable tool.

Impact of long-term operation of nuclear power plants on the marine ecosystem of Daya Bay

Based on the monitoring data of Daya Bay in 2011-2017, the impact of long-term operation of nuclear power plants (NPPs) on the marine ecosystem was accessed. ¹³⁷Cs and ⁹⁰Sr in seawater and sediment of Daya Bay decreased with time. The environmental half-lives of ¹³⁷Cs and ⁹⁰Sr in seawater, ¹³⁷Cs in sediment were 7.1 a, 11.7 a and 13.9 a, respectively. The total dose rates of the marine organisms ranged from 230.5 to 853.9 nGy/h, lower than the ERICA screening benchmark (10 μGy/h). ²¹⁰Po, ²²⁶Ra and ²³²Th were the main dose contributors. ¹³⁷Cs and ⁹⁰Sr contributed to ~0.01 %-~0.06 % of the total radiation. ¹³⁷Cs contributed to <0.6 ‰ of the committed effective dose for humans. There were almost no radiation effects on the marine ecosystem of Daya Bay from NPPs before 2017. In the future, there will be no radiation risk for the long-term discharge of low-level radioactive waste to Daya Bay.

Identification of areas of interest for radiological impact assessments in an evolving landscape context

Regulations concerning potential future health impacts of the final disposal of radioactive wastes in geological disposal facilities are written in terms of annual dose to individuals who are representative of small groups living in the landscape in the vicinity of the repository site. As disposal programmes in Sweden and Finland have progressed towards licensing and construction, so too has detail describing the state and evolution of surface biosphere and the landscape around the proposed disposal sites increased. Simple and generic biosphere dose assessment models in early iterations have grown in complexity with increasing site-specific detail that aims to capture the radiologically significant features of the landscape into which future releases of radionuclides might credibly occur. Current dose assessment models used in support of license applications for disposal programmes in Sweden and Finland are highly complex and their application consequently lacks transparency. An alternative simpler approach to characterising landscape objects for dose assessment models would be beneficial in that it would offer an additional line of reasoning and would add clarity, thereby supporting the decision-making process of the regulatory authorities. In the context of coastal Fennoscandia, landscape change is relatively rapid and dramatic with post-glacial landrise transforming areas of the coastal seabed into terrestrial ecosystems over a period of a few thousand years, global sea level rise notwithstanding. The locations of the geosphere-biosphere interfaces for deep geologic disposal can be estimated with some precision but the nature of the receiving ecosystems at the time of the release is less certain. The approach described here provides a statistical quantification of key morphological characteristics of areas in the landscape where doses could arise, so as to better express uncertainties in dose modelling. The proposed method assumes that the variation in the morphology of potential release locations can be described by the variation in landscape objects seen in the landscape on a wider scale, providing a statistical description of the possible landscape objects, so allowing a more comprehensive range of potential future evolutions to be addressed. Our understanding of the evolution of the landscape, based on the kinds of terrain and ecosystem development models used by POSIVA in Finland and SKB in Sweden, suggests that objects identified in present-day maps can be used as analogues for a statistical characterisation of objects in the future landscape; objects identified in the observed topography and bathymetry can therefore serve as the basis for the statistical description of landscape dose objects over the period during which doses are likely to arise. Using digital elevation models around a disposal site in Finland, we show that the statistical descriptions of landscape dose objects at three times over a period of 10 kyear of the evolved landscape are sufficiently similar to establish the suitability of the approach. The aim of this statistical analysis is to supplement current methods for defining radiological assessment models so as to provide additional numerical support to both the simpler and more complex methods employed by implementors and regulators. The method has been developed in the context of the Swedish and Finnish regulatory review process and is referred to in the IAEA's revised BIOMASS methodology. We briefly address how the method might be applied in other landscape contexts.

Radiological risk associated with 222Rn occurrence in groundwater sources of rural communities in the semiarid region of Paraíba, Brazil

Rural and isolated communities traditionally lack adequate water treatment and distribution systems, and water quality assessment often does not include radioactivity measurement. Here we present, for the first time, the results of Rn measurements and the evaluation of the associated dose in groundwaters of rural communities in a semiarid area in Paraiba State, Brazil. Water samples were analysed using a low-level liquid scintillation spectrometer (LSS). Radon concentrations were higher than EPA and WHO recommended levels in water for most of the wells (range of 5.5-1107.0 Bq/L, average 252.8 Bq/L). Higher Rn concentration was measured in deeper wells and located in area rich in granite and diorite rocks. The annual effective doses varied between 0.021 and 4.317 mSv/y for infants, 0.016-3.182 mSv/y for children, and 0.015-3.022 mSv/y for adults, exceeding, in some cases, the 1 mSv/y reference level recommended by the WHO and UNSCEAR for the public. Thus, water consumption from half of the wells should be avoided unless adequate treatment is provided. Results highlight the need to perform actions to supply water with appropriate quality to the local population.

Distribution of 241Am and Pu isotopes in the Curonian Lagoon and the south-eastern Baltic Sea seawater, suspended particles, sediments and biota

Distribution trends and temporal variations of 241Am and Pu isotopes in the south-eastern Baltic Sea during the study period of 1999-2001 and 2011-2015 were investigated with the aim to study temporal changes of radionuclide levels in seawater, suspended particles and sediment, to estimate 241Am and 239,240Pu levels in marine biota and to assess the radiation doses received by the biota. The activities of 241Am and 239,240Pu were measured by alpha spectrometry after radiochemical purification. 241Pu was determined radiometrically via the ingrown daughter 241Am after 10-12 years of storage, while the 240Pu/239Pu atom ratio of was measured by accelerator mass spectrometry. The 239,240Pu activities in suspended particles collected in the coastal waters of the Baltic Sea decreased by a factor of ∼3 during the study period, while they decreased about fourfold in the Curonian Lagoon. This could indicate a decrease in the influx of particles containing Pu isotopes into the Baltic Sea. While in the Curonian Lagoon, the 239,240Pu activities in the sediment samples varied insignificantly during the study periods, in the Baltic Sea, the maximum activity decreased by a factor of 6, and the mean/median values decreased by ∼4 times. The assessment tool ERICA was used to calculate the dose rates for biota. The total dose rate from all analysed radionuclides was <0.1 μGy/h, therefore no risk to organisms was identified.

Assessment of children's exposure to carbonaceous matter and to PM major and trace elements

Particulate matter (PM) pollution is one of the major environmental concerns due to its harmful effects on human health. As children are particularly vulnerable to particle exposure, this study integrates the concentration of PM chemical compounds measured in the micro-environments (MEs) where children spend most of their time to assess the daily exposure and inhaled dose. PM samples were analysed for organic and elemental carbon and for major and trace elements. Results showed that the MEs that contribute most to the children's daily exposure (80%) and inhaled dose (65%) were homes and schools. Results indicated that the high contribution of particulate organic matter (POM) indoors indicate high contributions of indoor sources to the organic fraction of the particles. The highest concentrations of PM chemical compounds and the highest Indoor/Outdoor ratios were measured in schools, where the contribution of mineral elements stands out due to the resuspension of dust caused by the students and to the chalk used in blackboards. The contribution of the outdoor particles to inhaled dose (24%) was higher than to the exposure (12%), due to the highest inhalation rates associated with the activities performed outdoor. This study indicates the importance of indoor air quality for the children's exposure and health.

Radiological monitoring in some coastal regions of the Saudi Arabian Gulf close to the Iranian Bushehr nuclear plant

We studied the concentrations of terrestrial and anthropogenic radionuclides in seawater and shore sediment/sand of three selected regions; Khafji, Safaniyah and Menifah along the Saudi Arabian Gulf coast. The mean activity concentrations of the ²²⁸Ra, ²²⁶Ra, and ⁴⁰K in the analyzed sand samples are 5.9, 3.5 and 113.5 Bq/kg, and the respective values in seawater samples are 1.6, 0.8 and 10.4 Bq/L. All data show lower than the corresponding UNSCEAR (2000) reported world average values of 35, 30 and 400 Bq/kg for soil matrix. A few relevant radiological hazards were quantified by the estimation of the absorbed dose rate, and the results are compared with the prescribed limits set by international regulatory bodies. Measured data indicates that the studied coastal regions pose a negligible radiological hazards to the public, and show an insignificant radioactive loading to this coastal region by the Busher nuclear power plant.

Development of a dynamic food chain model for assessment of the radiological impact from radioactive releases to the aquatic environment

The software tool POSEIDON-R was developed for modelling the concentration of radionuclides in water and sediments as well as uptake and fate in the aquatic environment and marine organisms. The software has been actively advanced in the aftermath of the Fukushima Dai-ichi accident. This includes development of an uptake model for the benthic food chain, a kinetic-allometric compartment model for fish and recent advancements for the application of ³H. This work will focus on the food chain model development and its extension to key artificial radionuclides in radioecology such as ³H. Subsequently, the model will be applied to assess the radiological dose for marine biota from ³H, ⁹⁰Sr, ¹³¹I, ¹³⁴Cs and ¹³⁷Cs released during and after the Fukushima Dai-ichi accident. The simulation results for ³H, ⁹⁰Sr, ¹³¹I, ¹³⁴Cs and ¹³⁷Cs obtained from the coastal box (4-4 km) located at the discharge area of the Fukushima Dai-ichi NPP, and the surrounding regional box (15-30 km) are compared with measurements. The predictions are by and large consistent with experimental findings, although good validation for ³H, ⁹⁰Sr and ¹³¹I is challenging due to lack of data. On the basis of the model predictions a dose assessment for pelagic and benthic fish is carried out. Maximum absorbed dose rates in the coastal box and the regional box are respectively 6000 and 50 μGy d^-1 and are found in the pelagic non-piscivorous fish. Dose rates exceeding ICRP's derived consideration levels of 1 mGy d^-1 are only found in the direct vicinity of the release and shortly after the accident. During the post-accidental phase absorbed dose rates consistently fall to levels where no deleterious effects to the marine biota are expected. The results also demonstrate the prolonged dose rate from ¹³⁴Cs and ¹³⁷Cs, particularly for benthic organisms, due to caesium's affinity with sediment, re-entry of caesium from the sediment into the food chain and external exposure from its high energetic gamma emissions. Uptake of non-organic tritium (HTO) and organically bound tritium (OBT) is modelled and shows some accumulation of OBT in the marine organism. However, dose rates from tritium, even during the accident, are low.

Support activities in Namie Town, Fukushima undertaken by Hirosaki University

This paper does not necessarily reflect the views of the International Commission on Radiological Protection.Several radiation monitoring research projects are underway on dose assessment, biological analysis, and risk communication under an agreement with Namie Town. Indoor radon and thoron progeny concentrations have been measured using passive-type monitors to estimate internal doses due to inhalation. In addition, airborne radiocaesium concentrations at five points in Namie Town have been analysed using a high-purity germanium detector to estimate internal doses for comparison with radon. External radiation doses from natural and artificial radionuclides have also been estimated using an in-situ gamma-ray spectrometer. Other support activities are mentioned briefly in this article.

Application of Bayesian statistics for radiation dose assessment in mixed beta-gamma fields

The present paper proposes a novel method, based on Bayesian statistics, as a new approach in the field of thermoluminescence dosimetry for the assessment of personal doses in mixed beta-gamma radiation fields. The method can be utilized in situations when the classical way of dose calculation is insufficient or impossible. The proposed method uses a prior function which can be assigned to the unknown parameter and the likelihood function obtained from an experiment, which together can be transformed into the posterior probability distribution of the sought parameter. Finally, the distribution is converted to the value of the dose. The proposed method is supported by analytical and Monte Carlo calculations, which confirmed the results obtained through the Bayesian approach.

The SHAMISEN Project: Challenging historical recommendations for preparedness, response and surveillance of health and well-being in case of nuclear accidents: Lessons learnt from Chernobyl and Fukushima

Experience suggests that current nuclear accident response planning in European countries mostly has a technical focus, with less attention paid to social, psychological and ethical issues. Information provided tends to be directed towards decisions made by experts, rather than for the support of affected populations. The SHAMISEN (Nuclear Emergency Situations - Improvement of Medical And Health Surveillance) consortium, composed of close to 50 experts from 10 countries, performed a critical review of current recommendations and experiences regarding dose assessment and reconstruction, evacuation decisions, long-term health surveillance programmes and epidemiological studies. The review included case studies and lessons drawn from the living conditions and health status of populations affected by the Chernobyl and Fukushima accidents, taking an integrative approach to health and well-being. Based on this work, SHAMISEN developed a series of comprehensive recommendations aimed at improving the preparedness, response, long-term surveillance and living conditions of populations affected by past or future radiation accidents, in a manner responding to their needs, while minimising unnecessary anxiety.

Lessons from past radiation accidents: Critical review of methods addressed to individual dose assessment of potentially exposed people and integration with medical assessment

The experiences of the Chernobyl and Fukushima nuclear accidents showed that dosimetry was the essential tool in the emergency situation for decision making processes, such as evacuation and application of protective measures. However, at the consequent post-accidental phases, it was crucial also for medical health surveillance and in further adaptation to changed conditions with regards to radiation protection of the affected populations. This review provides an analysis of the experiences related to the role of dosimetry (dose measurements, assessment and reconstruction) regarding health preventive measures in the post-accidental periods on the examples of the major past nuclear accidents such as Chernobyl and Fukushima. Recommendations derived from the review are called to improve individual dose assessment in case of a radiological accident/incident and should be considered in advance as guidelines to follow for having better information. They are given as conclusions.

210Po in Сrimean salt lakes

This paper presents the results of radioecological monitoring study of natural radionuclide ²¹⁰Po in 11 lakes located in different regions of the Crimean peninsula. These investigations of the Crimean salt lakes were conducted for the first time in the history. The main objectives of this work were: to determine the features of the ²¹⁰Ро behavior in the salt lakes ecosystems, as well as calculation of the doses received by the lakes hydrobionts from α-radiation of absorbed ²¹⁰Po. Concentrations of ²¹⁰Po in the water, suspended matter, the bottom sediments and biota were determined by radiochemical processing and α-spectroscopy measurements. The concentrations of dissolved ²¹⁰Po in the water of investigated lakes were in 0.9-327.1 times higher than in the Black Sea closest regions. The highest concentrations of ²¹⁰Po in water were determined in the lakes of the Kerchenskaya group. These lakes are located on the territory of Crimea where oil is produced. The ²¹⁰Ро activity concentrations in the bottom sediments from Crimean salt lakes were comparable with those of the Black Sea coastal zone. Concentration ratio (CR) of polonium in suspended matter ranged from 10 to 10⁴ for different lakes. A significant trend in a decrease of CR values of ²¹⁰Ро for suspended matter with increasing water salinity was revealed. High levels of ²¹⁰Po accumulation were noted for adult crustacean Artemia spp. (typical inhabitant of the Crimean saline lakes). The CR of ²¹⁰Po for adult Artemia spp. reached 10⁵ while the CR of this radionuclide by their cysts was significantly lower. The absorbed doses from ²¹⁰Po α-radiation calculated for adult Artemia spp. were more than 60 times lower than the permissible dose rate for biota (IAEA, 1992).The obtained results will be used to identify the biogeochemical peculiarities in behavior of the main dose-formative radionuclide ²¹⁰Po, in the water ecosystems with different salinity, including water reservoirs poorly studied in the radioecological aspect and having extreme condition for the existence of lots of species of hydrobionts, such as hypersaline Crimean lakes.

Activity concentrations of 210Po and 210Pb in fish and mussels in İzmir, Turkey, and the related health risk assessment (dose assessment and pesticide levels) to the consumers

The activity concentrations of natural radionuclides (²¹⁰Po and ²¹⁰Pb) and residual pesticide levels were determined from the fish (red mullet, common sole, anchovy, horse mackerel, gray mullet, and sardine) and mussel samples collected in İzmir Bay seasonally from October 2012 and July 2013. The ²¹⁰Po and ²¹⁰Pb concentrations varied between 5.7 ± 4.0 Bq kg^-1 dry weight (dw) to 353.7 ± 45.0 Bq kg^-1(dw) and 0.7 ± 0.2 Bq kg^-1 (dw) to 4.3 ± 0.8 Bq kg^-1 (dw), respectively. From a public health point of view, the fish and mussel collected from the İzmir Bay are not harmful to consumers.

Determination and distribution of 210Po in different morphological parts of tobacco plants and radiation dose assessment from cigarettes in Turkey

Both sides of tobacco leaves accumulate 210Po through their sticky hairs (trichomes) by means of diffusive deposition. It is known that tobacco leaves may contain high amounts of 210Po concentrations. However, there is less information about radionuclides in tobacco plants. In the study, the 210Po concentrations were determined monthly in different morphological parts of tobacco plants (leaf, stem, root) and soil samples and soil-to-plant transfer factor for 210Po was determined and the activity concentrations of 210Po radionuclide in 16 different popular brands of cigarettes were investigated in order to estimate the annual effective doses of 210Po to smokers. Besides the study investigated (focused on) the correlation between the amount of rainfall and 210Po concentration of tobacco leaf. The results of the present study indicated that the activity concentration of 210Po in cigarettes distributed in Turkey ranged from 16.1 ± 1.0 to 37.6 ± 2.6 mBq per cigarette and the mean value of their activity concentrations was 22.4 ± 1.5 mBq per cigarette. The mean value of annual effective doses of 210Po to smokers (20 cigarettes smoked by an individual per day) obtained from these activity concentrations was estimated to be 188.5 ± 12.4 μSv y-1.

Sobol sensitivity analysis for risk assessment of uranium in groundwater

The exposure to uranium (U) in the natural environment is primarily through ingestion (eating contaminated food and drinking water) and dermal (skin contact with U powders/wastes) pathways. This study focuses on the dose assessment for different age-groups using the USEPA model. A total of 156 drinking water samples were tested to know U level in the groundwater of the study region. Different age-groups were selected to determine the human health impact due to uranium exposure in the residing populations. To determine the relative importance of each input, a variance decomposition technique, i.e., Sobol sensitivity analysis, was used. Furthermore, different sample sizes were tested to obtain the optimal Sobol sensitivity indices. Three types of effects were evaluated: first-order effect (FOE), second-order effect (SOE) and total effect. The result of analysis revealed that 17% of the samples had U concentration above 30 µg l^-1 of U, which is the recommended level by World Health Organization. The mean hazard index (HI) value for younger age-group was found to be less than 1, whereas the 95th percentile value of HI value exceeded for both age-groups. The mean annual effective dose of U for adults was found to be slightly higher than the recommended level of 0.1 m Sv year^-1. This result signified that adults experienced relatively higher exposure dose than the children in this region. Sobol sensitivity analysis of FOE showed that the concentration of uranium (C_w) is the most sensitive input followed by intake rate (IR) and exposure frequency. Moreover, the value of SOE revealed that interaction effect of C_w- IR is the most sensitive input parameter for the assessment of oral health risk. On the other hand, dermal model showed C_w- F as the most sensitive interaction input. The larger value of SOE was also recorded for older age-group than for the younger group.

Evaluation of public dose from FHR tritium release with consideration of meteorological uncertainties

Tritium management is a potentially significant issue in fluoride-salt-cooled high-temperature reactors (FHRs), as these reactors can produce tritium at high rates. Potential impact of the tritium released into the environment needs to be investigated to help determine the maximum-allowable tritium-release rate from an FHR plant. In this study, a dose assessment on the public resulting from FHR tritium release was performed via computational modeling. Three potential locations for FHR construction, i.e., the Hanford site, Idaho Falls in Idaho, and Oak Ridge in Tennessee, were selected. Atmospheric tritium dispersion was modeled using computer code family GENII and a parametric study of key meteorological variables was carried out. An uncertainty analysis was performed to examine the reliability of the prediction of dose for the year 2020. It is discovered that conditions in favor of lower public dose level from FHR tritium release include low atmosphere temperature, high wind speed, high relative humidity, and high tritium release point. It is also discovered that for different geological locations, the dominance of meteorological parameters differs significantly. Among the three locations modeled, although the Hanford site might be the most suitable location for FHR construction in the past, in the near future, Oak Ridge would possess advantages in the dose assessment aspect over the other two. We assumed that the tritium release rate from an FHR plant is given at 18.5 TBq/day and compared the probability of the maximum individual dose exceeding the regulatory limit (0.4 mSv/y). According to the prediction of dose for the year 2020, this probability is extremely low. While for Idaho Falls, it is 91.62% and for the Hanford site, 44.27%. The results indicate that effective measures should be taken for tritium control in FHR.

Dose assessment for patients with stage I non-small cell lung cancer receiving passive scattering carbon-ion radiotherapy using daily computed tomographic images: A prospective study

BACKGROUND AND PURPOSE

This study aimed to assess dose distributions for stage I non-small cell lung cancer (NSCLC) with passive scattering carbon-ion radiotherapy (C-ion RT) using daily computed tomography (CT) images.

MATERIALS AND METHODS

We enrolled 10 patients with stage I NSCLC and acquired a total of 40 pre-fractional CT image series under the same settings as the planning CT images. These CT images were registered with planning CT images for dose evaluation using both bone matching (BM) and tumor matching (TM). Using deformable image registration, we generated accumulated doses. Moreover, the volumetric dose parameters were compared in terms of tumor coverage and lung exposure and statistical analyses were performed.

RESULTS

Overall, 25% of 40 fractional dose distributions were unacceptable with BM, compared with 2.5% with TM (P < 0.001). Using BM, three patients' accumulated dose distributions were unacceptable; however, all were satisfactory with TM (P < 0.001). No differences were observed in water-equivalent path length (WEL). The required margins in patients with poor dose distribution were 5.9 and 4.4 mm for BM and TM, respectively.

CONCLUSIONS

This study establishes that CT image-based TM is robust compared with conventional BM for both daily and accumulated dose distributions. The effects of changes in WEL seem to be limited. Hence, daily CT alignment is recommended for patients with stage I NSCLC receiving C-ion RT.

Investigations on chemical composition and natural radioactivity levels from salt water and peloid used in pelotherapy from the Techirghiol Lake, Romania

The work presents the historical evolution, objectives, goals, concepts, chemical and radiometric methods, results and conclusions for salt waters and natural peloids used in pelotherapy. This study assesses chemical composition, natural radioactivity concentrations and the radiological hazard in peloid and salt water samples, from ten places in the Techirghiol Lake from Romania. Pelotherapy is a very important procedure, and thus, the materials used for this purpose must be well characterized to guaranty safety use. Concentrations of elements such as Sr, Ba, Mn, Fe, Sb, Zn, Cu, Pb, Ti, Ni, Cr, As have been measured using ICP-OES analytical technique. The natural radionuclides such as ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been determined by gamma-ray spectrometry. The average activity concentrations were of 0.48 ± 0.10 Bq/kg for ²³⁸U, 0.60 ± 0.10 Bq/kg for ²²⁶Ra, 0.30 ± 0.08 Bq/kg for ²³²Th and 17.5 ± 1.3 Bq/kg for ⁴⁰K for salt water samples. Also, the mean activity concentrations for peloids were: 5.70 ± 1.00 Bq/kg for ²³⁸U, 6.85 ± 1.60 Bq/kg for ²³²Th, 15.3 ± 3.7 Bq/kg for ²²⁶Ra and 95.8 ± 5.5 Bq/kg for ⁴⁰K. The results from this study contribute to the identification of possible contaminants in the salt water and peloid, and their association with the potential ecological and human health risk. In this context, of using salt water and peloid in a relatively long treatment period, several radiological indices have been calculated, to determine if the radionuclide's content can be also harmful to human health. The assessment indicates that humans are not exposed to concentrations of metal contaminants higher than the international recommended values.

Organ and detriment-weighted dose rate coefficients for exposure to radionuclide-contaminated soil considering body morphometries that differ from reference conditions: adults and children

The system of protection established by the International Commission on Radiological Protection (ICRP) provides a robust framework for ionizing radiation exposure justification, optimization, and dose limitation. The system is built upon fundamental concepts of a reference person, defined in ICRP Publication 89, and the radiation protection quantity effective dose, defined in ICRP Publication 103. For external exposures to radionuclide-contaminated soil, values of the organ dose rate coefficient (Gy/s per Bq/m²) and effective dose rate coefficient (Sv/s per Bq/m²) have been computed by several authors and national laboratories using ICRP-compliant reference phantoms-both stylized and voxelized. These coefficients are of great value in post-accident exposure assessments as seen in Japan following the 2011 Fukushima Daiichi nuclear power station disaster. Questions arise, however, among the general public regarding the accuracy of organ and effective dose estimates based upon reference phantom methodologies, especially for those individuals with height and/or total body mass that differ modestly or even substantially from the nearest age-matched reference person. In this pilot study, this issue is explored through use of the extended 351-member UF/NCI hybrid phantom library in which values of organ and detriment-weighted dose rate coefficients are computed for sex/height/mass-specific phantoms, and systematically compared to their values of the effective dose rate coefficient computed using corresponding reference phantoms. Results are given for monoenergetic photons, and then for some 33 different radionuclides, with all dose rate coefficient data provided in a series of electronic annexes. For environmentally relevant radionuclides such as ⁸⁹Sr, ⁹⁰Sr, ¹³⁷Cs, and ¹³¹I, percent differences between the detriment-weighted dose rate coefficient computed using non-reference and the effective dose rate coefficient computed using reference phantoms vary only ± 5% for young children approximated by the reference 1-year-old phantom. With increased body size and age, the range of percent differences in these two quantities increases to + 7% to - 14% for the reference 5-year-old, to + 10% to - 27% for the reference 10-year-old, to + 33% to - 31% for the reference 15-year-old, and to + 15% to - 40% for male and female adults.

A modelling approach to assess the environmental/radiological impact of C-14 release from radioactive waste repositories

Assessments of the environmental impact of C-14 disposal often assume that C-14 is converted into gases that are able to migrate to the surface, where they pose a radiological risk. However, uncertainties, associated with the long-term release of C-14 from graphite and the evolution in the post-closure environment of a geological disposal facility (GDF), exist. In this paper, an integrated modelling framework has been developed to investigate these uncertainties. The modelling framework consists of a biogeochemical near field model which interfaces with a geosphere/biosphere model and it is verified by comparing the results to those obtained from other models. A sensitivity analysis discloses that a faster mid chain scission rate of stopped cellulose about four orders of magnitude assesses a twice higher effective dose. In another scenario, which is related to the control of microbial activity by pH and the availability of carbon dioxide to microbes, the effective dose is two orders of magnitude higher compared with a reference scenario. This modelling work illustrates also the importance of far field parameters, such as the rock permeability and the release area of gas pathway, to the assessment of effective dose.

A study of the protective actions for a hypothetical accident of the Bushehr nuclear power plant at different meteorological conditions

In this work, protective actions have been studied assuming a hypothetical severe accident of the Bushehr nuclear power plant at different meteorological conditions. Simulations of the atmospheric dispersion of accidental airborne releases were performed using the RASCAL code. Total effective dose equivalent (TEDE) and thyroid dose received by members of the public living within a radius of 40 km around the reactor site were calculated for various atmospheric stability classes and weather conditions. According to the results of the dose assessment and by following the protective action guide of the Environmental Protection Agency (EPA), the critical zone and appropriate protective actions were determined depending on various metrological conditions. It was found that, for atmospheric stability class F and calm weather conditions, the maximum distance from the site of release for which TEDE is greater than the corresponding dose limit and for which sheltering or evacuation response actions are required, is 11 km. For the same weather conditions, the corresponding maximum distance for which iodine prophylaxis is required is 32 km. Based on the present simulations, it can be concluded that the metrological condition has a great influence on the radionuclide atmospheric dispersion and, consequently, on the critical zone where protective actions are required after the assumed accident condition.

Simulation of radionuclide atmospheric dispersion and dose assessment for inhabitants of Tehran province after a hypothetical accident of the Tehran Research Reactor

Radiological dose assessment is one of the main categories of safety assessment for nuclear reactors and facilities. The radiation risks to the public and to the environment that may arise from these facilities have to be assessed and, if necessary, controlled. The main objective of this paper is the assessment of radiation doses to residents of Tehran province after a hypothetical accident of the Tehran Research Reactor (TRR) including the determination of any protective actions that might be needed for the benefit of people's health. The concentration of radionuclides in air and deposited on the ground surface as a result of a hypothetical radionuclide release from the TRR, following a hypothetical accident scenario, have been calculated by the HYSPLIT computer code. Simulations were performed using selected source terms taken from the TRR Final Safety Analysis Report (FSAR). Meteorological data of the Air Resources Laboratory of the National Oceanic and Atmospheric Administration (NOAA) have been used in these calculations. The simulation results indicate that maximum annual total effective dose equivalent values for the residents of the Tehran province are less than the protective action dose limits. Thus, it is concluded that during this hypothetical accident in the TRR, required safety due to public radiation is achieved and the residents of Tehran province are safe under a TRR accident condition.

Potential for recycling of slightly radioactive metals arising from decommissioning within nuclear sector in Slovakia

The decommissioning of nuclear installations represents a complex process resulting in the generation of large amounts of waste materials containing various concentrations of radionuclides. Selection of an appropriate strategy of management of the mentioned materials strongly influences the effectiveness of decommissioning process keeping in mind safety, financial and other relevant aspects. In line with international incentives for optimization of radioactive material management, concepts of recycling and reuse of materials are widely discussed and applications of these concepts are analysed. Recycling of some portion of these materials within nuclear sector (e.g. scrap metals or concrete rubble) seems to be highly desirable from economical point of view and may lead to conserve some disposal capacity. However, detailed safety assessment along with cost/benefit calculations and feasibility study should be developed in order to prove the safety, practicality and cost effectiveness of possible recycling scenarios. Paper discussed the potential for recycling of slightly radioactive metals arising from decommissioning of NPPs within nuclear sector in Slovakia. Various available recycling scenarios are introduced and method for overall assessment of various recycling scenarios is outlined including the preliminary assessment of safety and financial aspects.

Deterministic and Semiprobabilistic Modeling of the Committed Dose from Radionuclides and the Chemical Burden from Uranium in the New Zealand Diet

To support New Zealand's food safety monitoring, estimates of the current population exposure to ionizing radiation through diet are needed. To calculate the committed dose from radionuclide activities in the food chain, dietary modeling was undertaken for different age and gender groupings of the New Zealand population. Based on a published survey of radionuclide activity concentrations in the New Zealand diet, deterministic and semiprobabilistic models were constructed to derive estimates of the effective dose via the diet. Deterministic estimated annual doses across the different age and gender groupings ranged from a minimum of 48 to 66 μSv/year for teenage girls to a maximum of 126 to 152 μSv/year for adult males. Polonium-210 was the main contributor to ingested dose, with anthropogenic radionuclides contributing very little. For adults, seafood represented the most important source of exposure, with the contribution from this source decreasing for younger age groups. Results of the semiprobabilistic model identified a range of possible ingested doses, with 2.5 to 97.5th percentile ranges of 0.01 to 1.44 μSv/day for adults and 0.02 to 1.84 μSv/day for children. Estimated doses to the New Zealand population show similarities to those of other countries and fall within the expected global range. The current level of exposure to ionizing radiation in the diet does not represent an elevated health risk.

Sources of inflow and nature of redistribution of 90Sr in the salt lakes of the Crimea

At the first time for the period after the Chernobyl NPP accident the nature of the redistribution of the ⁹⁰Sr concentrations in components of the ecosystems of the salt lakes of the Crimea were identified and described. Concentration of ⁹⁰Sr in water of the salt lakes depends on the sources of the inflow this radionuclide into aquatic ecosystems and salinity level of lakes water. Until April 2014 the flow of the Dnieper river water through the Northern-Crimean canal was more important factor of contamination of salt lakes of the Crimea by ⁹⁰Sr, than atmospheric fallout of this radionuclide after the Chernobyl NPP accident. Concentrations of ⁹⁰Sr in water of the salt lakes of the Crimea exceeded 2.4-156.5 times its concentrations in their bottom sediments. The ⁹⁰Sr dose commitments to hydrophytes, which were sampled from the salt lakes of the Crimea have not reached values which could impact them during entire the after-accident period.

Analytical and quasi-Bayesian methods as development of the iterative approach for mixed radiation biodosimetry

The present paper proposes two methods of calculating components of the dose absorbed by the human body after exposure to a mixed neutron and gamma radiation field. The article presents a novel approach to replace the common iterative method in its analytical form, thus reducing the calculation time. It also shows a possibility of estimating the neutron and gamma doses when their ratio in a mixed beam is not precisely known.

A method for independent modelling in support of regulatory review of dose assessments

Several countries consider geological disposal facilities as the preferred option for spent nuclear fuel due to their potential to provide isolation from the surface environment on very long timescales. In 2011 the Swedish Nuclear Fuel & Waste Management Co. (SKB) submitted a license application for construction of a spent nuclear fuel repository. The disposal method involves disposing spent fuel in copper canisters with a cast iron insert at about 500 m depth in crystalline basement rock, and each canister is surrounded by a buffer of swelling bentonite clay. SKB's license application is supported by a post-closure safety assessment, SR-Site. SR-Site has been reviewed by the Swedish Radiation Safety Authority (SSM) for five years. The main method for review of SKB's license application is document review, which is carried out by SSM's staff and supported by SSM's external experts. The review has proven a challenging task due to its broad scope, complexity and multidisciplinary nature. SSM and its predecessors have, for several decades, been developing independent models to support regulatory reviews of post-closure safety assessments for geological repositories. For the review of SR-Site, SSM has developed a modelling approach with a structured application of independent modelling activities, including replication modelling, use of alternative conceptual models and bounding calculations, to complement the traditional document review. This paper describes this scheme and its application to biosphere and dose assessment modelling. SSM's independent modelling has provided important insights regarding quality and reasonableness of SKB's rather complex biosphere modelling and has helped quantifying conservatisms and highlighting conceptual uncertainty.

Calculations of individual doses for Techa River Cohort members exposed to atmospheric radioiodine from Mayak releases

Time-dependent thyroid doses were reconstructed for over 29,000 Techa River Cohort members living near the Mayak production facilities from ¹³¹I released to the atmosphere for all relevant exposure pathways. The calculational approach uses four general steps: 1) construct estimates of releases of ¹³¹I to the air from production facilities; 2) model the transport of ¹³¹I in the air and subsequent deposition on the ground and vegetation; 3) model the accumulation of ¹³¹I in environmental media; and 4) calculate individualized doses. The dose calculations are implemented in a Monte Carlo framework that produces best estimates and confidence intervals of dose time-histories. Other radionuclide contributors to thyroid dose were evaluated. The ¹³¹I contribution was 75-99% of the thyroid dose. The mean total thyroid dose for cohort members was 193 mGy and the median was 53 mGy. Thyroid doses for about 3% of cohort members were larger than 1 Gy. About 7% of children born in 1940-1950 had doses larger than 1 Gy. The uncertainty in the ¹³¹I dose estimates is low enough for this approach to be used in regional epidemiological studies.

Environmental gamma radiation analysis for Ulsan city with the highest nuclear power plant density in Korea

This study presents a real-time measurement-based rapid radiation distribution visualization system for radionuclide recognition, which can quickly scan a contaminated environment. The system combines a portable detector with a digital map and a program for quick data treatment. Radiation information at the measurement location is transferred between a detector and a laptop. It includes environmental and artificial components, specific radionuclides, and total radionuclides. After scanning the area, the radiation distributions are comprehensively displayed in 2D and 3D maps corresponding to the measured area, all in a few tens of seconds. The proposed method was verified using the standard ¹³⁷Cs and ⁶⁰Co sources. The gamma radiation distribution of the areas measured in Ulsan city, which included non-destructive testing and radioisotope treatment facilities, hospitals, transportation spots, and residential and commercial areas, showed that Ulsan city has maintained safe levels of radiation. The system performed well. In addition, it was found that this system could detect unexpected hot spots quickly in affected environments.

Radioactive impacts on nekton species in the Northwest Pacific and humans more than one year after the Fukushima nuclear accident

This study investigated the radioactive impacts on 10 nekton species in the Northwest Pacific more than one year after the Fukushima Nuclear Accident (FNA) from the two perspectives of contamination and harm. Squids were especially used for the spatial and temporal comparisons to demonstrate the impacts from the FNA. The radiation doses to nekton species and humans were assessed to link this radioactivity contamination to possible harm. The total dose rates to nektons were lower than the ERICA ecosystem screening benchmark of 10μGy/h. Further dose-contribution analysis showed that the internal doses from the naturally occurring nuclide ²¹⁰Po were the main dose contributor. The dose rates from ¹³⁴Cs, ¹³⁷Cs, ⁹⁰Sr and ^110mAg were approximately three or four orders of magnitude lower than those from naturally occurring radionuclides. The ²¹⁰Po-derived dose was also the main contributor of the total human dose from immersion in the seawater and the ingestion of nekton species. The human doses from anthropogenic radionuclides were ~ 100 to ~ 10,000 times lower than the doses from naturally occurring radionuclides. A morbidity assessment was performed based on the Linear No Threshold assumptions of exposure and showed 7 additional cancer cases per 100,000,000 similarly exposed people. Taken together, there is no need for concern regarding the radioactive harm in the open ocean area of the Northwest Pacific.

Assessment of natural radioactivity and gamma-ray dose in monazite rich black Sand Beach of Penang Island, Malaysia

Activity concentrations of primordial radionuclides in sand samples collected from the coastal beaches surrounding Penang Island have been measured using conventional γ-ray spectrometry, while in-situ γ-ray doses have been measured through use of a portable radiation survey meter. The mean activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K at different locations were found to be less than the world average values, while the Miami Bay values for ²²⁶Ra and ²³²Th were found to be greater, at 1023±47 and 2086±96Bqkg^{̶ 1} respectively. The main contributor to radionuclide enrichment in Miami Bay is the presence of monazite-rich black sands. The measured data were compared against literature values and also recommended limits set by the relevant international bodies. With the exception of Miami Bay, considered an elevated background radiation area that would benefit from regular monitoring, Penang island beach sands typically pose no significant radiological risk to the local populace and tourists visiting the leisure beaches.

Public member dose assessment of Bushehr Nuclear Power Plant under normal operation by modeling the fallout from stack using the HYSPLIT atmospheric dispersion model

In this work, public dose resulting from fission products released from Bushehr Nuclear Power Plant (BNPP) under normal operation is assessed. Due to the long range transport of radionuclides in this work (80 km) and considering terrain and meteorological data, HYbrid Single-Particle Lagrangian Integrated Trajectory (HYsplit) model, which uses three dimensional long-range numerical models, has been employed to calculate atmospheric dispersion. Annual effective dose calculation is carried out for inhalation, ingestion, and external exposure pathways in 16directions and within 80 km around the site for representative person. The results showed the maximum dose of inhalation and external exposure for adults is 3.8 × 10^-8Sv/y in the SE direction and distance of 600 m from the BNPP site which is less than ICRP 103 recommended dose limit (1 mSv). Children and infants' doses are higher in comparison with adults, although they are less than 1 mSv. Ingestion dose percentage in the total dose is less than 0.1%. The results of this study underestimate the Final Safety Analysis Report ofBNPP-1 (FSAR)data.

Impacts on the terrestrial environment in case of a hypothetical accident involving the recovery of the dumped Russian submarine K-27

Objects containing radioactivity have been routinely dumped in Arctic waters near NW Russia up until the 1990s. One of the most radioactive objects in this region, the nuclear submarine K-27, was dumped in Stepogovo Fjord and contained spent nuclear fuel (SNF). Although the two K-27 submarine reactors were mothballed before dumping, concerns about the potential long term risks of contamination remain and plans to retrieve and decommission K-27 exist. In this article, human dose and environmental impact aseessments are presented for two possible future scenarios involving: (1) an ingress of water into a reactor in situ leading to a spontaneous chain reaction (SCR) and (2) an on-board fire when SNF is being removed at the mainland decommissiong site at Gremhika Bay on the Kola Peninsula. Assessments have been completed using conservative assumptions, focusing on possible effects to Norwegian territory. Atmospheric transport and deposition of radioactivity was modelled near field and regionally, using appropriate models, whilst human doses and environmental exposures were modelled using a standard IAEA approach and the ERICA tool, respectively. Results indicate that large areas of Norwegian territory could be affected by fallout from the Gremhika scenario, especially in the north, though at levels two orders of magnitude lower than those observed after the Chernobyl accident. Potential doses, primarily due to ground shine, to a critical group of personnel on-site at Stepogovo resulting from a SCR could require preventative measures based on ICRP recommendations (20-100 mSv). Doses to non-human biota in Norway for the Gremhika scenario would be negligible, typical of background dose rates for terrestrial organisms.

Systematic influences of gamma-ray spectrometry data near the decision threshold for radioactivity measurements in the environment

Several methods for reporting outcomes of gamma-ray spectrometric measurements of environmental samples for dose calculations are presented and discussed. The measurement outcomes can be reported as primary measurement results, primary measurement results modified according to the quantification limit, best estimates obtained by the Bayesian posterior (ISO 11929), best estimates obtained by the probability density distribution resembling shifting, and the procedure recommended by the European Commission (EC). The annual dose is calculated from the arithmetic average using any of these five procedures. It was shown that the primary measurement results modified according to the quantification limit could lead to an underestimation of the annual dose. On the other hand the best estimates lead to an overestimation of the annual dose. The annual doses calculated from the measurement outcomes obtained according to the EC's recommended procedure, which does not cope with the uncertainties, fluctuate between an under- and overestimation, depending on the frequency of the measurement results that are larger than the limit of detection. In the extreme case, when no measurement results above the detection limit occur, the average over primary measurement results modified according to the quantification limit underestimates the average over primary measurement results for about 80%. The average over best estimates calculated according the procedure resembling shifting overestimates the average over primary measurement results for 35%, the average obtained by the Bayesian posterior for 85% and the treatment according to the EC recommendation for 89%.

Assessment of natural radioactivity and (137)Cs in some coastal areas of the Saudi Arabian gulf

The levels of natural radioactivity have been investigated in some Saudi Arabian Gulf coastal areas. Sampling sites were chosen according to the presence of nearby non-nuclear industrial activities such as, the two main water desalination plants in Al Khobar and Al Jubail, and Maaden phosphate complex in Ras Al Khair, to ensure that effluents discharges into the Arabian Gulf didn't enhance radioactivity in seawater and shore sediments. Seawater samples were analyzed for radium isotopes (Ra-226 & Ra-228) and measured by gamma spectrometry using high purity germanium detector, after radiochemical separation of the isotopes by co-precipitation with MnO2. Shore sediment samples were analyzed for (226)Ra, (228)Ra ((232)Th), (4)°K and (137)Cs using gamma sepectrometry. A small variation was observed in the activity concentrations of the investigated radioisotopes, and the activity levels were comparable to those reported in literature. Quality assurance and methods validation were established through the efficiency calibration of the detectors, the estimation of uncertainties, the use of blanks, the analysis of standard reference materials and the intercomparison and proficiency tests. Radiological hazards were assessed, and the annual effective dose had an average value of 0.02 mSv. On the basis of the current results, we may conclude that any radiological hazards to the public visiting these shores are not expected.

Should we ignore U-235 series contribution to dose?

Environmental Risk Assessment (ERA) methodology for radioactive substances is an important regulatory tool for assessing the safety of licensed nuclear facilities for wildlife, and the environment as a whole. ERAs are therefore expected to be both fit for purpose and conservative. When uranium isotopes are assessed, there are many radioactive decay products which could be considered. However, risk assessors usually assume (235)U and its daughters contribute negligibly to radiological dose. The validity of this assumption has not been tested: what might the (235)U family contribution be and how does the estimate depend on the assumptions applied? In this paper we address this question by considering aquatic wildlife in Canadian lakes exposed to historic uranium mining practices. A full theoretical approach was used, in parallel to a more realistic assessment based on measurements of several elements of the U decay chains. The (235)U family contribution varied between about 4% and 75% of the total dose rate depending on the assumptions of the equilibrium state of the decay chains. Hence, ignoring the (235)U series will not result in conservative dose assessments for wildlife. These arguments provide a strong case for more in situ measurements of the important members of the (235)U chain and for its consideration in dose assessments.

Post-closure biosphere assessment modelling: comparison of complex and more stylised approaches

Geological disposal facilities are the preferred option for high-level radioactive waste, due to their potential to provide isolation from the surface environment (biosphere) on very long timescales. Assessments need to strike a balance between stylised models and more complex approaches that draw more extensively on site-specific information. This paper explores the relative merits of complex versus more stylised biosphere models in the context of a site-specific assessment. The more complex biosphere modelling approach was developed by the Swedish Nuclear Fuel and Waste Management Co (SKB) for the Formark candidate site for a spent nuclear fuel repository in Sweden. SKB's approach is built on a landscape development model, whereby radionuclide releases to distinct hydrological basins/sub-catchments (termed 'objects') are represented as they evolve through land rise and climate change. Each of seventeen of these objects is represented with more than 80 site specific parameters, with about 22 that are time-dependent and result in over 5000 input values per object. The more stylised biosphere models developed for this study represent releases to individual ecosystems without environmental change and include the most plausible transport processes. In the context of regulatory review of the landscape modelling approach adopted in the SR-Site assessment in Sweden, the more stylised representation has helped to build understanding in the more complex modelling approaches by providing bounding results, checking the reasonableness of the more complex modelling, highlighting uncertainties introduced through conceptual assumptions and helping to quantify the conservatisms involved. The more stylised biosphere models are also shown capable of reproducing the results of more complex approaches. A major recommendation is that biosphere assessments need to justify the degree of complexity in modelling approaches as well as simplifying and conservative assumptions. In light of the uncertainties concerning the biosphere on very long timescales, stylised biosphere models are shown to provide a useful point of reference in themselves and remain a valuable tool for nuclear waste disposal licencing procedures.

Representative doses to members of the public from atmospheric releases of (131)I at the Mayak Production Association facilities from 1948 through 1972

Scoping epidemiology studies performed by researchers from the Southern Urals Biophysics Institute revealed an excess prevalence of thyroid nodules and an increased incidence of thyroid cancer among residents of Ozersk, Russia, who were born in the early 1950s. Ozersk is located about 5 km from the facilities where the Mayak Production Association produced nuclear materials for the Russian weapons program. Reactor operations began in June 1948 and chemical separation of plutonium from irradiated fuel began in February 1949. The U.S.-Russia Joint Coordinating Committee on Radiation Effects Research conducted a series of projects over a 10-year period to assess the radiation risks in the Southern Urals. This paper uses data collected under Committee projects to present examples of reconstructed time-dependent thyroid doses to reference individuals living in Ozersk from (131)I released to the atmosphere for all relevant exposure pathways. Between 3.22 × 10(16) and 4.31 × 10(16) Bq of (131)I may have been released during the 1948-1972 time period, and a best estimate is 3.76 × 10(16) Bq. In general, younger children incur greater thyroid doses from (131)I than adults. A child born in 1947 is estimated to have received a cumulative thyroid dose of 2.3 Gy for 1948-1972, with a 95% confidence interval of 0.51-7.3 Gy. Annual doses were the highest in 1949 and a child who was 5 years old in 1949 is estimated to have a received an annual thyroid dose of 0.93 Gy with a 95% confidence interval of 0.19-3.5 Gy.

Radiological characterization of tap waters in Croatia and the age dependent dose assessment

Activity concentrations of (234)U, (238)U, (226)Ra, (228)Ra, (210)Po and (210)Pb in tap waters, originating from various geological regions of Croatia, were determined. Activity concentrations of measured radionuclides are in general decreasing in this order: (238)U≈(234)U>(228)Ra≈(210)Pb>(226)Ra≈(210)Po. Based on the radionuclide activity concentrations average total annual internal doses for infants, children and adults, as well as contribution of each particular radionuclide to total dose, were assessed and discussed. The highest doses were calculated for infants, which makes them the most critical group of population. All values for each population group were well below the recommended reference dose level (RDL) of 0.1mSv from one year's consumption of drinking water according to European Commission recommendations from 1998. Contribution of each particular radionuclide to total doses varied among different age groups but for each group the lowest contribution was found for (226)Ra and the highest for (228)Ra.

Contemporary radioecological state of the North-western Black Sea and the problems of environment conservation

Review is devoted to the analysis of a radioecological situation in the North-western Black Sea and concerns the levels of contamination of the components of an ecosystem by the main artificial radioactive isotopes ((90)Sr, (137)Cs, (239,240)Pu). The long-term accumulation trends of these radionuclides were analyzed in components of the Black Sea ecosystem after the Chernobyl nuclear power plant accident. Zones that have an increased ability to accumulate these radioisotopes were revealed. The assessment of irradiation dose rates formed by (90)Sr, (137)Cs and (239,240)Pu in Black Sea hydrobionts was obtained. The strategy for biodiversity conservation and sustainable management of natural resources should include monitoring of the radioecological state of the marine ecosystems, and the formation of a complex of biogeochemical criteria for assessment of an ecological situation in the sea. This approach is important for marine protected areas, since it allows the formation of a basis for scientific and practical function.

Tumor vascular disruption using various radiation types

The feasibility of disrupting a tumor's vascular structure with various radiation types and radionuclides is investigated. Calculated absorbed dose profiles for photons and (4)He ions suggest that low-energy beta-gamma and alpha emitting radionuclides can deposit sufficient absorbed dose to disrupt a tumor's vascular structure while minimizing the dose outside the blood vessel. Candidate radionuclides uniformly distributed in microspheres are theoretically investigated with respect to their vascular disruption potential and to offer an alternative to (90)Y microsphere therapy. Requisite activities of candidate low-energy beta-gamma and alpha emitting radionuclides to facilitate vascular disruption are calculated.

Effective dose in percutaneous transhepatic biliary drainage examination using PCXMC2.0 and MCNP5 Monte Carlo codes

OBJECTIVES

To estimate the organ equivalent doses and the effective doses (E) in patient undergoing percutaneous transhepatic biliary drainage (PTBD) examinations, using the MCNP5 and PCXMC2 Monte Carlo-based codes.

METHODS

The purpose of this study is to estimate the organ doses to patients undergoing PTBD examinations by clinical measurements and Monte Carlo simulation. Dose area products (DAP) values were assessed during examination of 43 patients undergoing PTBD examination separated into groups based on the gender and the dimensions and location of the beam.

RESULTS

Monte Carlo simulation of photon transport in male and female mathematical phantoms was applied using the MCNP5 and PCXMC2 codes in order to estimate equivalent organ doses. Regarding the PTBD examination the organ receiving the maximum radiation dose was the lumbar spine. The mean calculated HT for the lumbar spine using the MCNP5 and PCXMC2 methods respectively, was 117.25 mSv and 131.7 mSv, in males. The corresponding doses were 139.45 mSv and 157.1 mSv respectively in females. The HT values for organs receiving considerable amounts of radiation during PTBD examinations were varied between 0.16% and 73.2% for the male group and between 1.10% and 77.6% for the female group. E in females and males using MCNP5 and PCXMC2.0 was 5.88 mSv and 6.77 mSv, and 4.93 mSv and 5.60 mSv.

CONCLUSION

The doses remain high compared to other invasive operations in interventional radiology. There is a reasonable good coincidence between the MCNP5 and PCXMC2.0 calculation for most of the organs.

Assessment of the radiological impact of gamma and radon dose rates at former U mining sites in Tajikistan

An assessment of the radiological situation due to exposure to gamma radiation, radon ((222)Rn) and thoron ((220)Rn) was carried out at former uranium (U) mining and processing sites in Taboshar and at Digmai in Tajikistan. Gamma dose rate measurements were made using various field instruments. (222)Rn/(220)Rn measurements were carried out with field instruments for instantaneous measurements and then discriminative (222)Rn/(220)Rn solid state nuclear track detectors (SSNTD) were used for longer representative measurements. The detectors were exposed for an extended period of time in different outdoor and indoor public and residential environments at the selected U legacy sites. The results showed that gamma, (222)Rn and (220)Rn doses were in general low, which consequently implies a low to relatively low radiological risk. The radiation doses deriving from external radiation (gamma dose rate), indoor (222)Rn and (220)Rn with their short-lived progenies did not exceed national or international standards. At none of the sites investigated did the average individual annual effective doses exceed 10 mSv, the recommended threshold value for the general public. A radiation hazard could be associated with exceptional situations, such as elevated exposures to ionizing radiation at the Digmai tailings site and/or in industrial facilities, where gamma and (222)Rn/(220)Rn dose rates could reach values of several 10 mSv/a. Current doses of ionizing radiation do not represent a hazard to the health of the resident public, with the exception of some specific situations. These issues should be adequately addressed to further reduce needless exposure of the resident public to ionizing radiation.